Transducers are used in all fields of industry ranging from portable electronic devices, optics, biotechnology, solar to the medical device field. These transducers, which include for example ultrasound, thermal, capacitive-sensing, impedance-sensing, optical and mechanical, or MEMS devices, enable a vast array of sensing and energy conversion applications. Such transducers are frequently provided in the form of a layer, i.e. a sheet. Sometimes the transducer is made directly from, for example, a layer or sheet of electrically active material, although in other cases the layer may comprise a plurality of sub-layers or strata that together provide the transducer's function. Examples of transducer layers include piezoelectric layers, light emitting layers such as LED and OLED, light sensitive layers such as solar cells, pressure-sensitive layers and capacitive-sensing layers. MEMS transducers used in e.g. motion sensing may also be provided in the form of a layer. Polyvinylidene fluoride, i.e. PVDF, and the related materials in the PVDF group that include PVDF co-polymers and PVDF ter-polymers are examples of electrically active, or even more specifically piezoelectric, materials that are provided in the form of a layer from which transducers can be made directly. Piezoelectric materials are used in some of the above applications since they are responsive to pressure, and vice-versa, contract or expand when an electrical field is applied. All these applications, however suffer from the need to make electrical contact with the transducer layer in order to convey electrical signals to and from the transducer.
One example of the above need arises in the medical device field as described in currently unpublished PCT application PCT/IB2015/052425. In this it is required to make electrical contact with a piezoelectric sensor that is ultimately attached to a medical device. In this example the piezoelectric sensor is responsive to ultrasound signals which are used to track the position of the medical device within an ultrasound field. This need to make electrical contact with a transducer may be aggravated by the need to attach the transducer to the curved surface of a medical device, such as the shaft of a catheter or needle, and to convey electrical signals thereto.
Electrical solders present an obvious solution to this need, but the thermal constraints imposed by the transducer itself often demand the use of more costly low-temperature solders. A range of conductive adhesives have also been developed for this purpose.
Patent application WO2013/148149A1 relates to photovoltaic modules and discloses a means for making electrical contact with photovoltaic cells. In some embodiments a pressure sensitive adhesive, i.e. PSA, is used to facilitate such contact with one side of the solar cell. Patent application US2011/0297219A1 also relates to photovoltaic devices and also discloses the use of a pressure sensitive adhesive for making electrical contact with one side of photovoltaic devices.
Document US2010/0090332A1 describes a ceramic chip assembly that includes a ceramic base, a plurality of external electrodes, a pair of cylindrical metal lead wires, and an insulating protection material. The pair of external electrodes is oppositely formed on both side surfaces of the ceramic base, respectively. The cylindrical metal lead wire has one end thereof electrically and mechanically connected to the external electrodes by an electrical conductive adhesive, respectively, and has an external diameter identical to or greater than the thickness of the ceramic base. The insulating protection material includes a pair of insulating films and an insulating coating layer.
Document JP61040071 describes a high-polymer piezoelectric member that has thin-film electrodes. A flexible electrode sheet includes a high-polymer film, a thin-film lead part connected to an electrode, and another electrode having a lead part connected to yet another electrode. One of the electrodes is attached to a piezoelectric member and is bonded to another of the electrodes by an electrically conductive adhesive. Some of the electrodes are connected together by bonding an electrically conductive adhesive-backed copper foil between them.
The present invention seeks to address drawbacks of the above and other known solutions to this and related problems.